Time-Resolved Ion Energy Distribution Functions in a HiPIMS Plasma Using a Retarding Field Analyzer

摘要

Using a two-gridded retarding field analyzer, time-resolved ion velocity distribution functions at boundary in a HiPIMS plasma have been investigated. A pre-ionized HiPIMS power supply was employed to sputter a carbon target at low operating pressure (0.09-0.27 Pa). It was found that the IVDFs of ions travelling perpendicular to the sampling grid can reasonably be fitted by a shifted Maxwellian distribution function, hence the ion density and the effective ion temperature, as well as the shifted velocity were obtained. During the pulse at the pressure of 0.09 Pa, the ion temperature and density changed from ～ 0.25 eV and 4 × 10~(16)m~(-3) to ～ 0.06 eV and 2×10~(16)m~(-3). Changing the analyzer's orientation revealed that ion temperature and shifted velocity are almost isotropic, whereas a well-defined maximum of the ion density was found in a direction perpendicular to the target. Ion temperatures of less than -0.1 eV and high shifted velocities of- 5-7 km/s can be achieved by operating the discharge at low pressure. This implies that lowering the operating pressure during the HiPIMS process may be beneficial for depositing high temperature phases of thin films on to thermal sensitive substrates.